Those moves led to a 2.9% jump in Japan's Nikkei stock average, closing at 14,607, its highest level since January 2008. The weaker yen is a boon to Japan, as it makes Japanese products cheaper overseas and means that foreign currency converts to more yen when companies bring the profits home to Japan.

The price of commodities including crude oil and gold fell as the dollar strengthened. Crude fell 35 cents to $96.04 a barrel in New York, a loss of 0.4%. Gold fell $32 to $1,436 an ounce, or 2.2%.

Nearly all companies in the S&P 500 have reported first quarter earnings. The average net income for companies in the index is expected to rise 5%, according to research firm S&P Capital IQ. But revenue has fallen short in many cases, suggesting that companies are mostly cutting expenses to post higher profits.

Some investors are worried that companies won't be able to keep cutting and profit growth will slow, but stocks have gone higher anyway.

"The talk at the end of April was company earnings are slowing ... and it seemed like we'd have another 'Sell in May,' " said Gary Flam, who manages stock portfolios at Bel Air Investment Advisors. "But clearly that's not been the case in the first ten days."

The S&P had risen every day since the beginning of the month until Thursday, when it fell six points. The Nasdaq is at 12-year highs.

Flam speculates that stocks are rising partly because of a shift this year in investor attitudes toward the market.

"The last few years, risk was defined as losing money," he said. "The last few months, it's been defined as not making money."

Dell climbed after activist investor Carl Icahn and another big investor fighting founder Michael Dell's offer to take the company private launched another broadside against the plan. In a letter to Dell's board, they proposed a deal that would keep the company public and pay shareholders cash or stock worth $12 a share. Dell rose 13 cents, or 1%, to $13.45.